Image reconstruction and Gestalt formation in human spatial vision

A sampling theoretical and experimental framework for the study of spatial vision is introduced. It is suggested that spatial Gestalt perception can be fruitfully analyzed by applying the concepts and methods of modern spatial filtering theory as they are known in the theory of image sampling and reconstruction. Demonstrations of the sampling processes in spatial vision are given and an experimental method for estimating the spatial reconstruction power of the human visual system is described. The experimental results presented suggest that high spatial frequency information has a special significance for human vision. Evidently, high frequency information is transmitted more easily through the visual system than has been generally assumed on the basis of contrast sensitivity studies.     

Audition dominates vision in duration perception irrespective of salience,attention, and temporal discriminability

Whereas the visual modality tends to dominate over the auditory modality in bimodal spatial perception, the auditory modality tends to dominate over the visual modality in bimodal temporal perception. Recent results suggest that the visual modality dominates bimodal spatial perception because spatial discriminability is typically greater for the visual than for the auditory modality; accordingly, visual dominance is eliminated or reversed when visual-spatial discriminability is reduced by degrading visual stimuli to be equivalent or inferior to auditory spatial discriminability. Thus, for spatial perception, the modality that provides greater discriminability dominates. Here, we ask whether auditory dominance in duration perception is similarly explained by factors that influence the relative quality of auditory and visual signals. In contrast to the spatial results, the auditory modality dominated over the visual modality in bimodal duration perception even when the auditory signal was clearly weaker, when the auditory signal was ignored (i.e., the visual signal was selectively attended), and when the temporal discriminability was equivalent for the auditory and visual signals. Thus, unlike spatial perception, where the modality carrying more discriminable signals dominates, duration perception seems to be mandatorily linked to auditory processing under most circumstances.     

Functional theory of illusory conjunctions and neon colors

Illusory conjunctions are the incorrect perceptual combination of briefly presented colors and shapes. In the neon colors illusion, achromatic figures take on the color of an overlaid grid of colored lines. Both illusions are explained by a theory that assumes (a) poor location information or poor spatial resolution for some aspects of visual information and (b) that the spatial location of features is constrained by perceptual organization. Computer simulations demonstrate that the mechanisms suggested by the theory are useful in veridical perception and they are sufficient to produce illusory conjunctions. The theory suggests mechanisms that economically encode visual information in a way that filters noise and fills in missing data. Issues related to neural implementation are discussed. Four experiments illustrate the theory. Illusory conjunctions are shown to be affected by objective stimulus organization, by subjective organization, and by the linguistic structure of ambiguous Hebrew words. Neon colors are constrained by linguistic structure in the same way as illusory conjunctions.     

Usage of spatial scales for the categorization of faces, objects, and scenes

The role of spatial scales (or spatial frequencies) in the processing of faces, objects, and scenes has recently seen a surge of research activity. In this review, we will critically examine two main theories of scale usage. The fixed theory proposes that spatial scales are used in a fixed, perceptually determined order (coarse to fine). The flexible theory suggests instead that usage of spatial scales is flexible, depending on the requirements of visual information for the categorization task at hand. The implications of the theories are examined for face, object, and scene categorization, attention, perception, and representation.     

Distinguishing the Senses

Seeing, hearing and touching are phenomenally different, even if we are detecting the same spatial properties with each sense. This presents a prima facie problem for intentionalism, the theory that phenomenal character supervenes on representational content. The paper reviews some attempts to resolve this problem, and then looks in detail at Peter Carruthers' recent proposal that the senses can be individuated by the way in which they represent spatial properties and incorporate time. This proposal is shown to be ineffective in distinguishing auditory from either visual or tactual perception, and substantial classes of visual and tactual perceptions are found that the posited spatial and temporal features fail to individuate.     

Object tracking and search in infancy: A review of data and a theoretical evaluation

Most research on infants' development of object and spatial concepts is based on object search tasks or visual tracking studies. In this review, it is concluded that many phenomena, particularly the tracking data, can be accounted for in terms of objective spatial perception in early infancy. However, some phenomena, particularly the stage IV search error, cannot be explained in these terms. A theoretical framework is put forward that integrates aspects of theory of direct perception with constructionist theory. First, it is proposed that objective properties of the basic spatial array are directly perceived, but that because perception is derived from action in the environment, there are initial limits to the scope and coherence of perception that diminish as the infant gains effective motor control. Second, it is proposed that in attempts to decipher the structure of social interchanges over objects, infants construct functional categorizations of objects that allow them to overcome limited awareness of their physical properties. Finally, it is suggested that these functional concepts provide an adequate means of interpreting the world, so that concepts based on the physical properties of objects, including their permanence, are relatively late developments.     

Visual perception of markings

Markings, such as designs, writings, diagrams, and depictions, are expressive and communicative human artifacts. The conventional assumption that findings from the study of the visual perception of markings—in particular, of pictures—can be generalized to real-world perception is examined and found to be false. The processes involved in the visual perception of the world and in the visual perception of markings differ in significant ways, and generalizations from one to the other must be undertaken with caution. The visual perception of markings is an identifiable and separate area of study. Implications for a general theory of the perception of markings are examined, and the perception of markings is contrasted with real-world perception.     

Testing the generality of the zoom-lens model: Evidence for visual-pathway specific effects of attended-region size on perception

There are volumes of information available to process in visual scenes. Visual spatial attention is a critically important selection mechanism that prevents these volumes from overwhelming our visual system’s limited-capacity processing resources. We were interested in understanding the effect of the size of the attended area on visual perception. The prevailing model of attended-region size across cognition, perception, and neuroscience is the zoom-lens model. This model stipulates that the magnitude of perceptual processing enhancement is inversely related to the size of the attended region, such that a narrow attended-region facilitates greater perceptual enhancement than a wider region. Yet visual processing is subserved by two major visual pathways (magnocellular and parvocellular) that operate with a degree of independence in early visual processing and encode contrasting visual information. Historically, testing of the zoom-lens has used measures of spatial acuity ideally suited to parvocellular processing. This, therefore, raises questions about the generality of the zoom-lens model to different aspects of visual perception. We found that while a narrow attended-region facilitated spatial acuity and the perception of high spatial frequency targets, it had no impact on either temporal acuity or the perception of low spatial frequency targets. This pattern also held up when targets were not presented centrally. This supports the notion that visual attended-region size has dissociable effects on magnocellular versus parvocellular mediated visual processing.     

Concurrent processing of spatial relations and objects in two cerebral hemispheres

This study examined hemispheric asymmetry for concurrent processing of object and spatial information. Participants viewed two successive stimuli, each of which consisted of two digits and two pictures that were randomly located and judged them as identical or different. A sample stimulus was presented in a central visual field, followed by a matching stimulus presented briefly in a left or right visual field. The matching stimuli were different from the sample stimuli with respect to the object (digit or picture) or spatial (locations or distances of items) aspect. No visual field asymmetry was found in the detection of object change. However, a left visual field advantage was found in the detection of spatial change. This result can be explained by the double filtering by frequency theory of Ivry and Robertson, who asserted that the left hemisphere has a bias for processing information contained in relatively high spatial frequencies whereas the right hemisphere has a bias for processing information contained in relatively low spatial frequencies. Based upon this evidence, the importance of interhemispheric integration for visual scene perception is discussed.     

Piaget's theory of space perception in infancy.

Piaget's theory of space perception in infancy is presented in the format of a hypothetico-deductive system. Eleven hypotheses are defined, regarding the perception of the agent of visual change; shape and size constancy; depth; and the perception of higher-order relationships among spatial elements. The proof Piaget offers for each hypothesis is presented in the following steps: behavioral evidence, interpretation in terms of inner states; inferences and generalizations. Presuppositions underlying the arguments are explicated. Critical notes are inserted whenever appropriate. Some general conclusions are briefly discussed.     

Voluntary head movement and allocentric perception of space

Although visual input is egocentric, at least some visual perceptions and representations are allocentric, that is, independent of the observer's vantage point or motion. Three experiments investigated the visual perception of three-dimensional object motion during voluntary and involuntary motion in human subjects. The results show that the motor command contributes to the objective perception of space: Observers are more likely to apply, consciously and unconsciously, spatial criteria relative to an allocentric frame of reference when they are executing voluntary head movements than while they are undergoing similar involuntary displacements (which lead to a more egocentric bias). Furthermore, details of the motor command are crucial to spatial vision, as allocentric bias decreases or disappears when self-motion and motor command do not match.     

Texture discrimination and the analysis of proximity.

A major theory of early visual processing has recently been proposed by Marr, which considers a number of aspects of visual perception in great detail, including grouping and texture discrimination. New phenomena associated with texture discrimination are described and experiments reported which allow a preliminary comparison of Marr's theory, as it applies to texture discrimination, with more established theories such as that due to Julesz. One experiment produced results which are clearly consistent with Marr's account, but the ability of his theory to deal with additional data on region suppression is not established. The theory of the analysis of proximity relations proposed by Fox offers a broadly satisfactory account of many texture perception results, while relying on the more fundamental parts of Marr's theory of primitive visual processes to deal with the remainder. A further attraction of proximity analysis is that it may shed new light on the classical paradox of symmetry perception. Some ways in which the preliminary proximity analysis model is incomplete are discussed, and it is concluded that development of the model may be profitable for theories of early visual processing.     

Relative brightness in natural images can be accounted for by removing blurry content

One critical question regarding visual cognition concerns how the physical properties of the visual world are represented in early vision and then relayed to high-level vision. Here, we posit a simple theory: Processes that encode object appearance reduce their response to spatial content that is coarser than the size of the attended object. We show that a filtering procedure based on this theory can account for the relative brightness levels of test patches placed in images of natural scenes and for many hard-to-explain brightness illusions. The implication is that the perception of brightness differences in most brightness illusions actually corresponds to physical differences present in the images. Portions of the visual system may encode these physical differences by means of neural processes that adaptively reduce their response to low-spatial-frequency content.     

A Theory of Perceptual Objects

Objects are central in visual, auditory, and tactual perception. But what counts as a perceptual object? I address this question via a structural unity schema, which specifies how a collection of parts must be arranged to compose an object for perception. On the theory I propose, perceptual objects are composed of parts that participate in causally sustained regularities. I argue that this theory falls out of a compelling account of the function of object perception, and illustrate its applications to multisensory perception. I also argue that the account avoids problems faced by standard views of visual and auditory objects.     

Object-based warping: an illusory distortion of space within objects

Visual objects are high-level primitives that are fundamental to numerous perceptual functions, such as guidance of attention. We report that objects warp visual perception of space in such a way that spatial distances within objects appear to be larger than spatial distances in ground regions. When two dots were placed inside a rectangular object, they appeared farther apart from one another than two dots with identical spacing outside of the object. To investigate whether this effect was object based, we measured the distortion while manipulating the structure surrounding the dots. Object displays were constructed with a single object, multiple objects, a partially occluded object, and an illusory object. Nonobject displays were constructed to be comparable to object displays in low-level visual attributes. In all cases, the object displays resulted in a more powerful distortion of spatial perception than comparable non-object-based displays. These results suggest that perception of space within objects is warped.     

Spatial patterns in tactile perception: is there a tactile field?

Previous studies of tactile spatial perception focussed either on a single point of stimulation, on local patterns within a single skin region such as the fingertip, on tactile motion, or on active touch. It remains unclear whether we should speak of a tactile field, analogous to the visual field, and supporting spatial relations between stimulus locations. Here we investigate this question by studying perception of large-scale tactile spatial patterns on the hand, arm and back. Experiment 1 investigated the relation between perception of tactile patterns and the identification of subsets of those patterns. The results suggest that perception of tactile spatial patterns is based on representing the spatial relations between locations of individual stimuli. Experiment 2 investigated the spatial and temporal organising principles underlying these relations. Experiment 3 showed that tactile pattern perception makes reference to structural representations of the body, such as body parts separated by joints. Experiment 4 found that precision of pattern perception is poorer for tactile patterns that extend across the midline, compared to unilateral patterns. Overall, the results suggest that the human sense of touch involves a tactile field, analogous to the visual field. The tactile field supports computation of spatial relations between individual stimulus locations, and thus underlies tactile pattern perception.     

Influences of the perception of self-motion on postural parameters.

We examined how spatial and temporal characteristics of the perception of self-motion, generated by constant velocity visual motion, was reflected in orientation of the head and whole body of young adults standing in a CAVE, a virtual environment that presents wide field of view stereo images with context and texture. Center of pressure responses from a force plate and perception of self-motion through orientation of a hand-held wand were recorded. The influence of the perception of self-motion on postural kinematics differed depending upon the plane and complexity of visual motion. Postural behaviors generated through the perception of self-motion appeared to contain a confluence of the cortically integrated visual and vestibular signals and of other somatosensory inputs. This would suggest that spatial representation during motion in the environment is modified by both ascending and descending controls. We infer from these data that motion of the visual surround can be used as a therapeutic tool to influence posture and spatial orientation, particularly in more visually sensitive individuals following central nervous system (CNS) impairment.     

Action potential influences spatial perception: Evidence for genuine top-down effects on perception

The action-specific account of spatial perception asserts that a perceiver’s ability to perform an action, such as hitting a softball or walking up a hill, impacts the visual perception of the target object. Although much evidence is consistent with this claim, the evidence has been challenged as to whether perception is truly impacted, as opposed to the responses themselves. These challenges have recently been organized as six pitfalls that provide a framework with which to evaluate the empirical evidence. Four case studies of action-specific effects are offered as evidence that meets the framework’s high bar, and thus that demonstrates genuine perceptual effects. That action influences spatial perception is evidence that perceptual and action-related processes are intricately and bidirectionally linked.     

La perception multisource : une nouvelle approche de la perception de scènes

Research conducted these last years in the field of spatial cognition report empirical findings that are difficult to account for with the traditional visual cognitive model of scene perception. One of the major contributions of these findings has been to invite rethinking scene perception, which would benefit from not being apprehended as centered mainly on the sensory modality considered. On the contrary, the Multisource model of scene perception developed by Intraub et al. offers an alternative theoretical framework considering visual perception as an act of spatial cognition, with spatial information at its core. According to this model, during the initial understanding of a view, the cognitive system would be elaborating a multisource representation, with spatial information constituting an egocentric framework that conveys to the observer a sense of the environment in which he/she is embedded. Scene representation would be organized around an amodal spatial structure combining different sources of information: a bottom-up and external source of information derived from different modalities (e.g., visual, haptic), as well as internal sources of high-level information (i.e., amodal, conceptual and contextual information). These different sources of information would work together to create a simulation of the likely environment, integrating the perceived view into a broader spatial context. Beyond rethinking scene perception, one of the advances of the model is to unify different fields of cognition apprehended until then in isolation. The current paper aims to present this model and some of the results it allows to account for.